The present invention pertains to reducing the transmission of emissions from internal combustion engines to the atmosphere; more particularly, the present invention pertains to reducing both the nitrogen oxide (NOx) and particulate matter (PM) emissions from engines.
Diesel internal combustion engines are known for their excellent fuel efficiency and durability. For these two reasons, diesel engines are the preferred power plants for commercial transportation vehicles both in the United States and around the world. Diesel engines have also become popular for use in passenger cars and in light-cargo applications such as pick-up trucks and sport utility vehicles.
The open chamber, direct-injection design internal combustion diesel engine is known for its superior fuel economy and high torque characteristics. However, as with many other fossil fuel burning engines, diesel internal combustion engines have come under increasingly tight exhaust emissions standards, which tight exhaust emissions standards have been mandated by various government administrative agencies.
Specifically, five pollutants in diesel engine exhaust emissions are regulated by government mandated standards: unburned hydrocarbons, carbon monoxide, nitrogen oxide, particulate matter, and smoke.
Modern diesel internal combustion engines of the direct-injection design emit extremely low concentrations of unburned hydrocarbons (HC), carbon monoxide (CO), and smoke. However, the nitrogen oxide (NOx) and particulate matter (PM) emissions still remain a challenge to diesel engine combustion and control engineers. The challenge for diesel engine combustion and control engineers in dealing with NOx and PM emissions results from the well-studied relationship between these two components of diesel engine exhaust, a relationship known in the diesel engine design and manufacturing industry as the NOx/PM tradeoff. In general, the NOx/PM tradeoff teaches that efforts to reduce NOx are generally detrimental to PM, and vice-versa.
Recently, three major factors have worked together in concert to provide an incentive to advance the state-of-the-art for controlling the NOx and PM emissions from diesel engines. These factors are:
The introduction of new emissions standards requiring substantial NOx reduction without any reduction in PM standards;
The introduction of new engine control technologies using advanced electronic systems;
The introduction of new exhaust after treatment devices having the potential for high NOx reduction. While diesel engine combustion and control engineers continue to strive to introduce engine design changes to meet ever tighter government mandated emissions standards, it is becoming clear that engine design changes alone may not be sufficient to meet new and projected standards. It is expected by those of ordinary skill in this art area that help in meeting tighter government mandated emissions standards will come from new advanced electronically-controlled engine operation management systems together with novel after treatment for emissions. Despite these expectations, the current state of the art has not yet provided a solution that meets the challenge of regulations on the amount of NO, and PM in diesel engine emissions.
Accordingly, a significant need remains in the art for a system which will reduce both the nitrogen oxide (NOx)and particulate matter (PM) emissions from diesel internal combustion engines released into the atmosphere.
The system of the present invention reduces both the nitrogen oxide (NOx) and the particulate matter (PM) emissions from a diesel internal combustion engine released into the atmosphere.
The disclosed integrated system for reducing the Nitrogen oxide (NOx) and the particulate matter (PM) emissions from an internal combustion engine released into the atmosphere includes an integration of three technologies that heretofore have never been used together in a single system. Specifically, the disclosed integrated system combines:
i) a cooled exhaust gas recirculation (EGR) system which removes a portion of the exhaust gas flow and recirculates the removed portion of the exhaust gas flow to be inserted into the stream of air taken into the diesel engine;
ii) a selective catalytic reduction (SCR) system placed in connection with the cooled exhaust gas recirculation system described above; and
iii) a diesel particulate filter (DPF) for collecting particulate matter placed in series connection downstream from the selective catalytic reduction system.